A material for medical use applied to a medical appliance such as an embolus treatment coil, a clip, a catheter, a stent, or a guide wire requires characteristics such as biocompatibility, corrosion resistance, and workability. Regarding these requirements, for example, stainless, a Co—Cr alloy, and a Pt—W alloy have been practically used as a metal material (see Patent Document 1).
Recently, with the widespread of inspection and therapy using a magnetic resonance image diagnosis apparatus (MRI) in a medical practice, there is a growing concern over an influence on an interaction between constituent materials of the medical appliance and an electromagnetic field in a magnetic field environment. Examples of material characteristics considering the magnetic field environment include magnetic susceptibility. The magnetic susceptibility of the material is problematic because it can be a factor of an artifact of the MRI. The artifact due to the magnetic susceptibility magnetizes a metal in a magnetic field to cause distortion or the like of an MRI image in a peripheral region of the magnetic field. The occurrence of the artifact hinders accurate surgery and diagnostic. The material for medical use with practical examples has high magnetic susceptibility and thus cannot suppress the artifact.
There are a small number of development examples of an alloy in consideration of an artifact-free. For example, Patent Document 2 discloses a development example of a stent which is applied with an Au—Pd alloy or an Ag—Pd alloy and is compatible with the MRI.